Graphene oxide-silver nanowires composites for protection against modern pollution - electromagnetic waves

With the development of the electronic industry, telecommunication, transportation, energy storage devices, and wireless technologies, the need for materials that are able to block electromagnetic waves (EMWs) in low-frequency regions of the spectrum is increasing. A new type of pollution named pollution by EMWs is an inevitable component of modern life. Although materials efficient in blocking the propagation of EMWs are developed, these materials show drawbacks regarding durability and mechanical properties, as well as a high production price and processability. Thus, new eco-friendly and durable materials are needed. Herein, we produced composites based on graphene oxide and silver nanowires to create an efficient shielding barrier for low frequencies (0-15 GHz) EMWs

Measurement of EMI shielding perfomance of graphene oxide – silver nanoparticles composites

Silver nitrate has been exposed to low-dose (1–20 kGy) gamma irradiation in the presence of graphene-based material (graphene oxide or electrochemically exfoliated graphene) to form silver nanoparticles (Ag NPs). The successful nucleation and growth of Ag NPs, which produce the evenly covered graphene surface, are made possible by the vast surface area of those graphene-based materials as well as the presence of oxygen-containing functional groups on the surface. With a significant size distribution of 10–50 nm for graphene oxide and 10–100 nm for electrochemically exfoliated graphene, the produced Ag NPs were spherical. We also performed ElectroMagnetic Interference (EMI) shielding performance measurements of these materials. EMI shielding performance measurement revealed relatively good performance of the EEG material whereas GO material does not show EM shielding.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Ultrasound assessment of the effect of fetal position on supine to prone righting reflex in the guinea pig fetus

The aim of the study was to assess the effect of guinea pig fetal position on the righting reflex from a supine to prone position using ultrasound examination. Experimental and control group were formed, each encompassing 20 pregnant females with 50 fetuses from the 31st to 66th day of gestation. During ultrasound examination, the fetuses from the experimental group were brought into a supine position relative to gravity by placing the dams in the appropriate position. In the control group fetuses were examined for changes in position irrespective of gravity as well as for changes in position after having been brought into a prone position relative to gravity. Comparison of the experimental and the control group showed that experimental group fetuses in the oldest bracket rotated successfully to a prone position more frequently than at other ages. The observed fetal movements indicate that the fetus changes its position using the contact-righting reflex

Measurement of EMI shielding performance of graphene oxide and electrochemically exfoliated graphene thin films

Graphene and its derivatives have become the scientific community's focus due to their remarkable electronic, mechanical, and optical properties. In this work, we prepared two graphene-based materials, graphene oxide (GO) and electrochemically exfoliated graphene (EEG), and performed morphological and structural analysis. Both materials showed good dispersibility in water. GO is composed of mainly single- and few-layer graphene sheets, while EEG is predominately multi-layer graphene. EEG showed better thermal stability under nitrogen flow compared to GO. We also performed ElectroMagnetic Interference (EMI) shielding performance measurements of these materials

New Records of Bruchidius Spermaphagous Species in Albizia julibrissin and Laburnum anagyroides and Their Parasitoid Complex in Serbia

Background and Purpose: Bruchidius villosus feeding in seed of Laburnum anagyroides, and Bruchidius terrenus seed pest of Albizia julibrissin are first recorded and completely new seed-beetle to Serbian Bruchinae fauna. This Chrysomelids which were found in Republic of Serbia during intensive studies from 2012 to 2014 are likely related to a mostly Paleotropical group, including also members of genera Bruchidius, Megabruchidius and Acanthoscellides. These seed-beetles develop in pods of these two woody legumes, widely grown ornamental trees and shrubs. Several recent reports reveal that this species are well established in France, Hungary, and Bulgaria. Materials and Methods: Bruchine and their legume hosts were observed by extensive field sampling throughout Serbia over three years and by rearing the beetles from the samples in the laboratory. Bruchines and the parasitoids were mass-reared in climate controled rooms under conditions close to those of their area of origin: 12:12 L:D, 3-23 °C and ≤80 % RH (depends of host plant ongoing phenology or experimental needs-proof of weevil monophagous feeding preferences). For the purpose of analyzing the observed phenomena (its intensity and relevance), some of the standard methods of statistical analysis and conclusion have been used. Results: Levels of seeds infestation still in the pods were high and comparable to other studies. Bruchine beetle infestation in the dehiscent fruits of host plants may be greater after the seeds and pods drop to the ground, as bivoltine generation occurs, but this has yet to be tested. Hypotheses on the geographic origin of this new species are also discussed. The effect of native parasitoids occurrence could potentially be interesting, given that their appearance suggest their specialization on the Bruchidius beetle species which is a common seed-predator on the leguminous seeds. Conclusions: The establishment of this new species is investigated using both morphological data and idioecological analyses. For this purpose, a methodology was developed to assess weevil field densities in a natural environment. However, this needs to be more carefully tested with a larger sample size and experiments. Significant levels of infested seed, leads to the conclusion that these seed parasites could be an important reducing factor of generative reproducing host plant potential

The influence of selenium and deiodinases blockers on juvenile rats body weight

In this work there was investigated the influence of selenium and deodinases blockers on juvenile rats body weight during three months. The experiment was carried out on 64 rats divided into eight groups with eight individual animals per group. Following groups were formed: 1. Se+PTU-IA- (control group), 2. Se+PTU+IA+, 3. Se+PTU+IA-, 4. Se+PTU- IA+, 5. Se-PTU-IA-, 6. Se-PTU+IA+, 7. Se-PTU+IA- and 8. Se-PTU-IA+. The groups labeled (Se+) were selenium adequate and they were fed with food that contained 0.334 mg Se/kg. The groups labeled (Se-) were selenium deficient and obtained food with 0.031 mg Se/kg. As deiodinases blockers there were used propylthiouracil (PTU+) in a dose of 150 mg/L of drinking water and iopanoic acid (IA+) in a dose of 6 mg/100 g TM intraperitoneally. Body weight of experimental rats was measured every seven days. After three weeks of treatment there were taken blood samples of animals from all experimental groups and following parameters were determined: selenium concentration in blood, thyroxine (T4), triiodothyronine (T3) and thyroidstimulating hormone (TSH) in blood plasma. Analysis of the samples showed that the animals from the groups treated with PTU had lower body weight in regard to the control group, as well as lower concentration of T3 and T4 in plasma. Selenium deficient rats had lower average body weight compared to the selenium adequate ones after three weeks, but there were no differences in thyroid hormones concentration. The lowest average body weight was noticed in selenium deficient rats groups treated with PTU. [Projekat Ministartsva nauke Republike Srbije, br. TR31050 i br. TR31003

Cultural Adaptation and Examination of Metric Characteristics Shirom-Melamed Burnout Questionnaire (SMBQ) On a Sample of Pharmacists in Serbia

Introduction: Due to the nature of work in pharmacies pharmacists may occur job burnout, which can affect the quality of health services. It is necessary to use validated instruments to test the burnout. One type of instrument is Shirom-Melamed Burnout Questionnaire (SMBQ). Objective: The primary objectives of this work are: cultural adaptation and assessment metric characteristics of SMBQ in a population of pharmacists in Serbia. Alternative objective is evaluate the degree of burnout in the pharmacist population. Methods: For comparison Maslach Burnout Inventory (MBI) was used. All licensed pharmacists have received an email by the Pharmaceutical Chamber of Serbia, with a link for accessing the questionnaires. The questionnaires were completed by 514 pharmacists. Results and Discussion: Professional translators carried out the translation using translation steps like forward translation and backward translation. Were calculated following metric characteristics: alpha - reliability coefficient Cronbach and associates; beta - the reliability of the first principal component; psi 1 - representativeness; h1 - the homogeneity (the average correlation of scale items), extent of curvature, horizontal (Skewness) and vertical (Kurtosis). Correlations between subscales are examined. Latent structure SMBQ (maximumlikelihud extraction) is examined. To select a number of factors, the method of parallel analysis was used. For calculation number of latent factors the Hull method was applied. Concurrent validity was examined by correlating the results of the questionnaire SMBQ and MBI. To confirm a one factor solution of the scale, factor analysis was used. Conclusion: All methods show that it is best to keep only one factor. SMBQ satisfies theoretical statistical criteria of reliability and validity and can be used to estimate job burnout at pharmacist population

Some Indicators of Beech Forests Vitality in the Republic of Serbia in Period 2004-2009

Background and purpose: Forests monitoring is one of the largest forest bio-monitoring systems that is carried out in order to record changes by using the most important environmental parameters. The National Focal Centre for forest monitoring in the Republic of Serbia, within the Institute of Forestry of the Republic of Serbia has been taking an active part in an international program of ICP Forest, with a view to improving its working activities and harmonizing them with other approaches to monitoring forests and forest ecosystems. Material and methods: In order to determine forest ecosystem processes, it is necessary to carry out detailed research of ecological and socio-economic consequences of forest deterioration and to study the impacts of regional climate changes on forest communities. In the period from 2004 to 2009, observations were performed on 130 sample plots and data necessary for further analysis were collected. These plots are systematically arranged in either a 16x16 km or a 4 x 4 km grid system. The main parameters assessed on the sample plots are the degree of defoliation and discolouration as well as the extent of damage. A comparative analysis of the data obtained in this period will provide a better insight into the present state of beech forests in Serbia as well the effects of defoliation and discolouration trends. Results and conclusion: Beech is the most common broadleaved tree species on the Level I sample plots. Its health state is the result of adverse effects of complex factors of abiotic and biotic origin (i.e. effects of both living organisms and complex natural processes within the beech forests habitats). This paper presents some indicators of beech forest vitality whose occurrence show certain regularity and which can be interpreted as a trend. The annual values of the health state elements and the fluctuations of these parameters from year to year present important indicators of vitality of beech forests in Serbia

Uticaj selena i blokatora dejodinaza na telesnu masu juvenilnih pacova

In this work there was investigated the influence of selenium and deodinases blockers on juvenile rats body weight during three months. The experiment was carried out on 64 rats divided into eight groups with eight individual animals per group. Following groups were formed: 1. Se+PTU-IA- (control group), 2. Se+PTU+IA+, 3. Se+PTU+IA-, 4. Se+P-TU-IA+, 5. Se-PTU-IA-, 6. Se-PTU+IA+, 7. Se-PTU+IA- and 8. Se-PTU-IA+. The groups labeled (Se+) were selenium adequate and they were fed with food that contained 0.334 mg Se/kg. The groups labeled (Se-) were selenium deficient and obtained food with 0.031 mg Se/kg. As deiodinases blockers there were used propylthiouracil (PTU+) in a dose of 150 mg/L of drinking water and iopanoic acid (IA+) in a dose of 6 mg/100 g TM intraperitoneally. Body weight of experimental rats was measured every seven days. After three weeks of treatment there were taken blood samples of animals from all experimental groups and following parameters were determined: selenium concentration in blood, thyroxine (T4), triiodothyronine (T3) and thyroidstimulating hormone (TSH) in blood plasma. Analysis of the samples showed that the animals from the groups treated with PTU had lower body weight in regard to the control group, as well as lower concentration of T3 and T4 in plasma. Selenium deficient rats had lower average body weight compared to the selenium adequate ones after three weeks, but there were no differences in thyroid hormones concentration. The lowest average body weight was noticed in selenium deficient rats groups treated with PTU.U okviru ogleda je ispitivan uticaj selena i blokatora dejodinaza na telesnu masu juvenilnih pacova tokom tri nedelje. Ogled je izveden na 64 pacova podeljenih u osam grupa od po 8 jedinki. Formirane su sledeće grupe: 1. Se+PTU-IA- (kontrolna grupa), 2. Se+PTU+IA+, 3. Se+PTU+IA-, 4. Se+PTU-IA+, 5. Se-PTU-IA-, 6. Se-PTU+IA+, 7. Se-PTU+IA- i 8. Se-PTU-IA+. Grupe sa oznakom (Se+) su bile selenadekvatne i dobijale su hranu koja je sadržala 0,334 mg Se/kg hrane. Grupe sa oznakom (Se-) su bile selendeficitne i dobijale su 0,031 mg mg Se/kg hrane. Kao blokatori dejodinaza su korišćeni propiltiouracil (PTU+) u dozi od 150 mg/L vode za piće i jopanoična kiselina (IA+) u dozi od 6 mg/100g t.m. intraperitonealno. Telesna masa oglednih pacova je merena svakih sedam dana. Nakon tri nedelje tretmana uzeti su uzorci krvi životinja iz svih oglednih grupa i određivani su sledeći parametri: koncentracja selena u punoj krvi, tiroksin (T4), trijodtironin (T3) i tireostimulirajući hormon (TSH) u krvnoj plazmi. Analiza je pokazala da su jedinke iz grupe tretiranih sa PTU imale nižu telesnu masu u odnosu na kontrolnu, kao i nižu koncentraciju T3 i T4 u plazmi. Selendeficitni pacovi su nakon tri nedelje imali nižu prosečnu telesnu masu u odnosu na selenadekvatne, ali nisu uočene razlike u koncentraciji tireoidnih hormona. Najniža prosečna telesna masa zabeležena je kod selendeficitnih grupa pacova tretiranih sa PTU